Human T-lymphotropic virus type II RFLP subtypes a0 and b4/b5 are associated with different demographic and geographic characteristics in the United States

Human T-lymphotropic virus type II (HTLV-II) prevalence is very low among t he general U.S, population, intermediate among American Indians, and high a mong injecting drug users and their sexual partners. However, the transmiss ion dynamics underlying this distribution are not well described. We obtain ed blood specimens from 493 blood donors found to be seropositive for HTLV- II at blood centers in five U.S, cities. Nested polymerase chain reaction w as used to amplify a 672-bp region of the HTLV-II long terminal repeat regi on, and restriction fragment length polymorphism (RFLP) analysis was perfor med to classify each virus into subtypes as defined by Switzer et al. (1995 , J. Virol. 69, 621-632). Associations between RFLP subtype and other chara cteristics were analyzed using multivariable logistic regression. HTLV-II s ubtype a0 was independently associated with age over 30 years (odds ratio ( OR) = 2.12, 95% confidence interval (CI) 1.13-3.99) and with Black race/eth nicity (OR = 2.00, 95% CI 1.10-3.65 versus Hispanic race/ethnicity). Conver sely, HTLV-II RFLP subtypes b4 and b5 were significantly more common among American Indian (OR = 3.77 95% CI 1.23-11.57) and Other race/ethnicity (OR = 4.22, 95% CI 1.25-14.27 both versus Black race/ethnicity) and at the Okla homa City blood center (OR = 3.57 95% CI 1.08-11.84 compared to Washington, DC/Baltimore). There may have been at least two transmission foci of HTLV- II in the United States: a modest HTLV-II subtype a0 epidemic of unknown so urce in the 1960s and 19708 spread predominantly among Black persons in sev eral geographic areas and a smaller focus of HTLV-II subtypes b4/b5 among n on-Black individuals in Oklahoma and perhaps in other areas not examined by this study, (C) 2001 Academic Press.